1. Field of the Invention
The present invention relates to a method for detecting, in lith type film or photographic printing paper or the like, the image area, i.e. the necessary light-transmissible or reflecting area or detecting unnecessary light-transmissible or reflecting areas and providing an opaque layer on the areas other than the necessary light-transmissible or reflecting area or on the unnecessary light-transmissible or reflecting areas to make the unnecessary light-transmissible areas opaque, as well as to an apparatus therefor. Further, the invention relates to an apparatus for detecting, in an image formed on lith type film or photographic printing paper, the necessary light-transmissible or reflecting area at a detecting pitch meeting with the picture element unit and opaquing other light-transmissible or reflecting areas, i.e. unnecessary light-transmissible or reflecting areas.
2. Description of the Prior Art
As the opaquing method or stopping out of lith type films or photographic printing papers or the like which is a work for making opaque to the unnecessary light-transmissible or reflecting areas (defective areas) appearing due to the adhesive agent, the stain of blockcopy layout sheet or stain of light exposing device or a work for classifying image areas by color, mask sheet method and opaque ink coating method have hitherto been known. Examples of the unnecessary light-reflecting area include black staines on a white ground, such as those in positive photographic printing paper. In the mask sheet method, a peelable red colored layer formed on polyethylene terephthalate film is cut into desired shape and superposed on the object to stop out the object. In the mask sheet method, the sheet is cut so as to meet with the size of lith film or photographic printing paper, registering pinholes are provided, and then it is put to use. This mask sheet method is very simple and convenient, because the unnecessary light-transmissible or reflecting areas can be made opaque rapidly by cutting the mask sheet while retaining it so as to meet with the registered position of lith film or photographic printing paper and then peeling off the red colored layer. If desired, two or three mask sheets are superposed, whereby a finer opaquing work can be practised. However, this method is disadvantageous in that the opaquing work is almost always a manual work so that the use of mask sheet increases the number or works, the cutting and peeling works are difficult to practise, and the scattering of light caused by the thickness of mask sheet deteriorates the quality of manuscript and letters formed from the lith type film or photographic printing paper. Further, it is unsuitable for opaquing the unnecessary light-transmissible or reflecting areas, because of high cost of mask sheet and low workability of this method.
In the opaque ink method, an opaque ink (stopping out ink) prepared by dispersing an opaque agent such as carbon black into a vehicle is used. This method is superior to the mask sheet method in that the formed opaque layer is small in thickness. This method is desclosed in Japanese Patent Kokai Gazette (Laid-Open) Nos. 91236/81, 6850/82 and 108853/82, for example. Although the methods disclosed therein are superior to the prior opaque ink methods in that a hard film can be formed and the visual evaluation of coated areas can be facilitated by mat effect, it is a manual work using a hair pencil so that fine opaquing work is difficult to practise and the work is laborious.
As opaquing methods other than the mask sheet method and the opaque ink method, the masking paper method which comprises applying a previously colored adhesive tape to the area to be stopped out and the method which comprises applying a light-untransmissible or unreflecting sheet (e.g. paper) to lith film or photographic printing paper can be referred to. All these opaquing methods by application are much disadvantageous in that they are very laborious manual works although they can realize the opaquing, they can correct only a large area. Thus these methods are used in the practical plate-making works only in some limited cases.
As above, in the prior means for opaquing the unnecessary light-transmissible or reflecting areas in lith film or photographic printing paper, almost all the works have been carried out by human hand, and all the improvement thereof so far studied are nothing other than a mere reinforcement of opaque or a means applicable only to limited cases.
As for the detection of unnecessary light-transmissible or reflecting areas in lith films and photographic printing papers or the like, the prior means therefor has been a visual detection by the use of human eyes, which is disadvantageous in that it takes a long period of time and it requires a skillfulness. In many case, the unnecessary light-transmissible or reflecting areas are pinholes, stains or lines. Such unnecessary areas are many in number and their detection is quite laborious at the present stage. In many cases, the areas to be stopped out are found in the small areas between letters and patterns.
As for the apparatus for detecting the unnecessary light-transmissible or reflecting areas in lith type films and photographic printing papers, printed matter testing apparatus and printing circuit testing apparatus can be referred to. In these apparatuses, the standard sample of test is converted to an image by television camera or the like, the image is memorized by an electronic (or electric) memory device, and image of each actual sample is compared with that of standard sample by scanning method or other appropriate method.
Such apparatuses are mentioned in Japanese Patent Kokai Gazette (Laid-Open) Nos. 250957/85, 250958/85, 12341/86, 12343/86 and 12345/86, for example. Although these apparatuses are advantageous in that they can rapidly and stably practise the test or input of information for the test and can realize a rationalized production of printed matters, they cannot detect the unnecessary light-transmissible or reflecting areas in lith type films and photographic printing papers, because there is no standard sample for these defects, i.e. the standard sample is the blockcopy layout sheet unusable in the test. Thus, it has been desired to developed an apparatus for opaquing the unnecessary light-transmissible or reflecting areas without referring to the standard sample.
Further, an apparatus which can stop out an area smaller than the size of picture element of image has been desired.
Thus, a mere combination of prior opaquing method and known printing matter testing apparatus is insufficient in functionality when used for detection of the unnecessary light-transmissible or reflecting areas in lith type films or photographic printing papers, and such a combination is technically difficult to operate. Further, such an apparatus is expensive.